1. Field of the Invention.
The instant invention relates to a mandrel assembly for rotatably supporting an orbiting cutting tool adjacent to the end of a hollow workpiece, such as a pipe or tube. The cutting plane, defined by the rotating cutting tool, is adjustable with respect to the central axis of the workpiece to enable the workpiece to be cut at an angle.
2. Brief Description of the Prior Art.
Many types of portable lathes have been developed over the years to machine the end of a hollow workpiece such as a pipe or tube. It is necessary to accurately machine and sometimes bevel the end face of the pipes or tubes in order to enable them to be welded together. Typically, these portable lathes comprise a mounting base having means thereon to be attached to the pipe, a mandrel rigidly attached to the mounting base, a cutting tool mechanism rotatably supported by the mandrel such that a cutting tool orbits about the longitudinal axis of the mandrel, and means to feed the cutting tool into the end face of the pipe. Mounting bases may either be internal, wherein it is attached to the inner surface of the pipe, or external wherein it is attached to the outer periphery of the pipe.
It is also known to provide adjustment means between the mounting base and the mandrel to enable the longitudinal axis of the mandrel to be adjusted with respect to the mounting base in order to accurately align this longitudinal axis with the central axis of the pipe. This enables the cutting tool to accurately machine the end face of the pipe to be perpendicular to the central axis of the pipe.
In some instances, however, it may be necessary to machine the end face of the pipe such that its plane is not perpendicular to the central axis. This is often necessary when assembling pipe lines in the field, since the pipe sections meant to be affixed together may be misaligned. In these instances, the mitering of the end face of the pipes is the only practical way to achieve a leak-proof joint between them.
It has been proposed to provide a portable lathe with a mandrel having the capability of adjusting the angle of the cutting plane with respect to the central axis of the workpiece to thereby miter the end of the workpiece in U.S. Ser. No. 406,540 to Nall et al. filed on Aug. 9, 1982 and entitled "Adjustable Mandrel For Supporting Tubular Workpieces". In this device, however, the angular adjustment of the mandrel with respect to the mounting base is limited to a single plane containing the longitudinal axis of the mounting base. While this device has proven successful, there remains a need for a portable lathe apparatus which will permit the angular adjustment of the mandrel with respect to the mounting base in any direction.